Jigs are one of the most common separators used in the known process for separating heavy minerals or ores from lighter gangue. The "Harz Jig" is one of the older types of jigs and includes a submerged fixed screen through which water is pulsed as the ore and gangue moves across the screen, causing the lighter gangue to flow along the surface of the water over the screen and the heavier ores to gravitate down and through the screen. The "Hancock Jig" utilizes an oscillating screen in a tank of water whereby a tray is given a combined horizontal and vertical reciprocating motion which causes the ore and gangue to pass rapidly over the screens, with the lighter gangue moving over the screen and the heavier material passing through the screen.
Previously, jigs were used widely for concentrating and washing base metal ores. Jigs are simple in operation and can be constructed locally with low cost to the owner and little maintenance. The use of jigs today, however, is slowly diminishing due primarily to the fact that power and water consumptions are high in known jigs and the tailing losses are generally higher than in other separating processes.